SAN JOSE -- When the San Francisco 49ers' stadium opens next month in Santa Clara, almost all of it will be new except for one thing: the water used to irrigate the field and flush the toilets.

Like hundreds of other places around Silicon Valley -- golf courses, power plants, San Jose's airport -- Levi's Stadium will use recycled water, which is essentially sewage that has been filtered, cleaned and disinfected.

Valley water officials on Friday will take a big step toward expanding the use of recycled water when they cut the ribbon at a $72 million high-tech water plant in Alviso. The plant will produce billions of gallons of highly purified water for Santa Clara County over the next decade. They hope to mix it with groundwater and, perhaps one day, serve it directly to the public to drink.

"It's a drought-proof supply," said Jim Fiedler, chief operating officer of the Santa Clara Valley Water District, which built and owns the plant.

"When people are asked at first about recycled water, they might say 'I don't think so,'" he said. "But when you give them more information about the technology, they accept it as a water supply."

Once derided as "toilet to tap," recycled water has been a regular feature in San Jose since 1997. It now makes up 5 percent of Santa Clara County's water supply, although it's only for non-potable uses such as watering grass at parks. The goal over the next decade is to double its use, city of San Jose and water district officials say.

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That, they add, would reduce the South Bay's reliability on water from the Sacramento-San Joaquin Delta, whose pumping can varying widely year-to-year depending on the endangered fish count, failing levees, lawsuits and droughts.

"This is water we don't have to import," said Kerrie Romanow, San Jose's director of environmental services. "It's a resource we have control over."

The new plant, called the Silicon Valley Advanced Water Purification Center, has not been without problems. When the water district broke ground in 2010 on five acres of city-owned land along Zanker Road, the project was supposed to be finished in 2012 and cost $52 million. But construction delays, price disagreements with the company supplying the micro-filtration equipment, and a decision to change electrical suppliers slowed work and drove up costs by $20 million.

But the plant is now running. And the water coming out -- after being zapped with a barrage of micro-filtration devices, reverse osmosis equipment and ultra-violet lighting -- meets state drinking water standards, though it is used now only for irrigation and industry.

No California water district serves recycled sewage water to the public to drink. State laws written years ago before technological advances don't permit it, although a feasibility study that could change that is due out in 2016 from the state Water Resources Control Board.

State rules do allow recycled water to replenish groundwater that is later used for drinking, as Orange County has done since 2008. Santa Clara Valley Water District officials say they hope to do that within five years -- and, if the new plant is successful, expand it, following a major public education campaign.

"The yuck factor is still real," said Tim Quinn, executive director of the Association of California Water Agencies. "While there is a psychological yuck, there is not a technical yuck. We have the technology to make it as clean as other drinking water or cleaner. It's perfectly safe."

Rick Simoes of San Jose said this week he would only drink the water in a pinch, but he supported using it for irrigation. "That makes total sense. Why use fresh water for irrigation when you don't need to?"

Both San Jose residents Zach Ulrich and Gigi Dawson, however, said they would be willing to drink recycled water that met state drinking water standards.

"As long as it's been purified and filtered," Dawson said. "Take out all the bad stuff. Don't give me cancer!"

Astronauts on the International Space Station already have equipment that turns urine into drinking water by boiling the water off, collecting the vapor -- like distilled water -- and then mixing it with water from air condensation and treating it with filters.

Only one American city so far is following suit. Wichita Falls, Tex., a community of 104,000 people north of Dallas, is so crippled by drought that it won approval from Texas health officials this year to use recycled water for drinking.

There, sewage goes through the city's wastewater plant, where it is further cleaned with microfilters, reverse osmosis and ultraviolet lighting to remove bacteria and pathogens. Then it is sent to a drinking water treatment plant, mixed with chlorine and fluoride and sent to faucets.

Currently, sewage from 1.5 million Santa Clara County residents is sent to the San Jose-Santa Clara Regional Wastewater Facility in Alviso. It is treated to the highest levels in the U.S. -- so-called tertiary treatment -- where it is settled, broken down with bacteria, filtered and disinfected. Most of the 95 million gallons a day is then released into San Francisco Bay.

But the city also sends about 15 million gallons a day through 142 miles of purple pipe and sells it to 748 customers, ranging from San Jose City Hall to Great America, Silver Creek Golf Course and tech companies like Oracle and Cisco. Wastewater plants in Palo Alto, Gilroy, Antioch and Sunnyvale also generate recycled water.

The new San Jose plant won't immediately increase the amount of recycled water. Rather, it will further purify the existing stream, reducing its salt content by a third. That, water district officials hope, will attract more customers such as Silicon Valley "clean rooms" and property owners with concerns about possible impacts of salt on redwoods and other sensitive landscaping.

The recycled water isn't cheap -- about $1,100 an acre-foot to produce, or roughly triple what it costs to buy water from the Delta, yet still about half the cost of desalinating ocean water.

The water district paid the bulk of the plant's cost, with the city of San Jose contributing $11 million. Next, it plans to seek state approval to blend the purified water with groundwater. Other cities may follow suit, experts say, but are looking for state lawmakers to put funding for recycled water projects in the water bond proposed for the November ballot.

"We've got to manage all of the water supplies in California as efficiently as we can," said Martha Davis, a board member of the California Water Reuse Association. "Using water only one time is wasteful."